JPS5833335B2 - How to control groundwater level - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling groundwater level by pumping water in a pumping well.

Conventionally, when performing ground excavation work, pumping wells are installed in the ground around earth retaining walls to pump up water to lower the groundwater level, reduce or prevent water pressure, earth pressure, or flooding, and improve workability.

This method can simply lower the groundwater level and improve flow direction when excavating a narrow area of the ground, but when excavating a wide area of the ground, it is not enough to simply lower the groundwater level. Therefore, it is necessary to control the groundwater level in the surrounding area to balance the water level and prevent unbalanced forces from acting on the excavated area.

To do this, the amount of water pumped from the many pumping wells installed around the excavation area must be controlled based on the difference between the underground water level during dark times and the target water level, and the operation of the pumping wells and Management is complicated and it is difficult to increase work efficiency without using special methods.

This invention was made with attention to this point, and its purpose is to maintain the groundwater level at a target value by pumping water from a large number of pumping wells while individually controlling the amount of water pumped based on the local water level. This provides a groundwater level control method that enables automated operation.

Examples will be described below with reference to the drawings.

In FIGS. 1 and 2, a steel pipe sheet pile 2 is built around a circular excavation section 1, and a plurality of wells W1, W2,...W13 are installed in a substantially circular shape outside of the steel pipe sheet pile 2. and four observation wells AI along the outer edge of the steel pipe sheet pile 2.
A2, A3, and A4 are provided.

Earthen pressure and water pressure act on the steel pipe sheet pile 2 surface of the side wall of the excavation section 1 from the outside.

The groundwater level 3 before pumping is high and a large water pressure acts on the steel pipe sheet pile 2, but the water level 4 after pumping becomes low and the acting water pressure can be reduced.

In addition, this water pressure is balanced around the excavation portion 1 to prevent unbalanced force from acting on the steel pipe sheet pile 2.

Observation wells A1...A4 are provided at intervals at the outer edge of the steel pipe sheet pile 2 where it is necessary to detect and check the groundwater level, and can detect the groundwater level.

The water level in the observation well has a slope toward the pumping well, and changes depending on the amount of water pumped in the pumping well Wm, but the relationship is complex as it is affected by the shape of the surrounding ground, strata, obstacles, etc. It is not required theoretically.

Therefore, each pumping well Wm is experimentally pumped, and the influence coefficient K, which is the relationship between the pumped water amount and the amount of water level change in each observation well An, is determined.

picture.

. Observation well 6 "0 standard change amount L/Pumped water amount QWm of pumping well Wm Also, the water level change amount Ln of each observation well An is calculated by the following formula.

L1= 1□Q W1+ K21 Q W2+...
...K13.1QW13L2 = Kt 2 Q
W2 + K22 QW2+・・・・・・・・・K13
．． 2QW13L4 = K14 QW1+ K24 Q
W2+...K13.4QWl3 In order to control the groundwater level using the pumping well Wm and the observation well An, which have the above relationship, first, the four observation wells AI, A2. A3. Groundwater level is detected at A4.

This water level is input to the water level converter 5, and the difference therebetween is converted into a signal using the target underground water level as a reference.

For example, +1m is +IV. Let O be O and -1m be -1■.

This is then input to the computing unit 6, but the computing unit 6 contains the pumping amount of the pumping wells W1...Wl3 and the observation well A.
I.

A2. A3. The coefficient determined from the relationship with the amount of water level change in A4 is stored in the circuit. If operation is performed in this state, each observation well AI, A2, A3. Based on the electrical signals input from A4 through the converter 5 moment by moment, the calculator determines whether the amount of pumped water in each pumping well W1...Wl3 is high or low, and the signal is used to control the pump flow rate. Send to device 7.

The pump 8 provided in each pumping well Wm performs pumping operation by controlling the pumping amount by this pump flow rate control device 7,
The groundwater level of the observation well An is maintained at the target value.

In actual operation, when the water level of the observation well An changes from the target groundwater level, it is operated so as to approach the target value.

Therefore, the degree of influence of the pumped water amount of each pumping well Wm on the water level of each observation well An is △v1. Δ■2 . . . Δ■13 are calculated from the influence coefficients and set in the calculator 6, and water is pumped preferentially from the pumping well Wm with a larger value.

In addition to the method of controlling the groundwater level as a whole by combining a plurality of pumping wells Wm and a plurality of observation wells An as described in the above embodiment, it is also possible to create a plurality of groups each consisting of one observation well and a pumping well and use these groups as a unit. It is also possible to control the groundwater level.

For example, a group is created with observation well A1 and three pumping wells W1, W2, and W3 that are located in the vicinity and have a large influence on water level changes, that is, have a large influence coefficient Kmn, and similarly (A2-W4. W5゜W6 ), (A3
-W7, W8, W9), (A4W10, Wl
1, Wl 2, Wl 3).

Within each group, as in the previous example, the influence coefficient is determined between the observation well An and the pumping well Wm by experiment, and the local sewage level is measured at the observation well An, and based on the difference from the target water level, each pumping well Control the groundwater level by pumping Wm.

By controlling the groundwater level similarly in each group, the groundwater level can be maintained at the required target value over a wide range.

This groundwater level control system is as described above, and when a pumping well is provided around the excavation part to pump up water and lower the groundwater level in the surrounding ground, an observation well is provided to detect the groundwater level.

Then, each pumping well is pumped in advance, and the influence coefficient (amount of change in water level of the observation well/amount of water pumped from the pumping well) of the amount of pumped water on the amount of water level change in each observation well is determined. Detect and read the difference from the target groundwater level.

Based on this water level difference and the above-mentioned influence coefficient, each pumping well controls the amount of water pumped, thereby controlling the groundwater level.

This method detects the groundwater level using an observation well installed separately from the pumping well, and inputs the experimentally determined influence coefficient of the pumping well into a calculator to control the amount of water pumped from each pumping well. Pump water.

As a result, the groundwater level at each location can be accurately maintained at the target value, preventing unbalanced forces from acting, and making it possible to automate the pumping management operation, resulting in significant labor savings. I can do it.

By forming a group by combining an observation well with a nearby pumping well that has a large effect on the water level, the relationship between the observation well water level and the pumping amount of the pumping well can be simplified, making it easier to set operating conditions and control the pumping amount. can be simplified.

[Brief explanation of the drawing]

Figure 1 is an overall layout of the excavation area and surrounding pumping wells and observation wells, Figure 2 is a cross-sectional view of Figure 1, and Figure 3 is a water level control system diagram of the pumping well, observation well, and observation well. . 1...Excavation section, 2...Steel pipe sheet pile, 3.
... Groundwater level before pumping, 4 ... Groundwater level after pumping, 5 ... Water level converter, 6 ... Arithmetic unit, 7 ... Pump flow rate control device, 8...
・Pump, AI, A2, A3, A4...
Observation well, Wl, W2. ...Wl3...
・Pumping well.

Claims (1)

[Claims] 1. When lowering the groundwater level in the ground around the excavated area by pumping water from multiple pumping wells around the excavated area, it is necessary to set up an observation well separate from the pumping wells and pump water from each pumping well in advance so that the amount of water pumped can be measured at each level. The influence coefficient on the water level change in the observation well is determined, and on the other hand, the difference between the groundwater level detected at the current observation well water level and the target groundwater level is determined, and each pumped water amount is determined based on this water level difference and the above-mentioned influence coefficient. A groundwater level control method characterized by controlled pumping.